Add minimal test

tests/tests_explainer/tests_tree_explainer/test_tree_treeshapiq.py

@@ -3,7 +3,7 @@
 import numpy as np
 import pytest
 
-from shapiq.explainer.tree import TreeModel, TreeSHAPIQ
+from shapiq.explainer.tree import TreeModel, TreeSHAPIQ, TreeExplainer
 
 
 def test_init(dt_clf_model, background_clf_data):
@@ -132,3 +132,28 @@ def test_edge_case_params():
     # test with max_order = 0
     with pytest.raises(ValueError):
         _ = TreeSHAPIQ(model=tree_model, max_order=0)
+
+def test_no_bug_with_one_feature_tree():
+    # create the dataset
+    X = np.array(
+        [
+            [1, 1, 1, 1],
+            [1, 1, 1, 2],
+            [2, 1, 1, 1],
+            [3, 2, 1, 1],
+        ]
+    )
+
+    # Define simple one feature tree
+    tree = {
+        "children_left": np.array([1, -1, -1]),
+        "children_right": np.array([2, -1, -1]),
+        "features": np.array([0, -2, -2]),
+        "thresholds": np.array([2.5, -2, -2]),
+        "values": np.array([0.5, 0.0, 1]),
+        "node_sample_weight": np.array([14, 5, 9]),
+    }
+    tree = TreeModel(**tree)
+    explainer = TreeExplainer(model=tree, index="SV", max_order=1)
+    shapley_values = explainer.explain(X[2])
+    print(shapley_values)